Hearing and understanding conversations in a dynamic environment can be very difficult. The brain uses several cues to help it focus on the sound source you are trying to listen to while trying to suppress the sounds you want to ignore. Social situations can be very dynamic. They often consist of multiple people talking, music and other background noise coming from items such as silverware or dishes. Our brain compares all of those sound sources by detecting time and volume differences at which they meet our ears.
Interaural Time Differences (ITD) is difference between when a sound source reaches one ear compared to the other. For example, if a sound source was on the right hand side, it would reach the right ear quicker than the left ear because it has less distance to travel. Interaural Level Differences (ILD) is the same as the ITD except that the volume level is compared across the ears. When the ear detects a sound source coming from the right hand side, the volume level, would be louder on the right compared to the left because a sound’s volume level dissipates over the distance it travels. It would have to travel a longer distance to reach the left ear than the right.
There are several studies that show significant differences in a normal hearing individual’s ability to detect ITDs and ILDs compared to the ability of individuals with hearing loss. Individuals with hearing loss have greater difficulty detecting ITDs and ILDs when there are competing sound sources, such as background noise. When that happens, the background noise is not as easily suppressed by the brain causing it to focus almost as equally on the undesired background noise as the desired speech signal. These findings further support investing in hearing devices with higher levels of technology so that a greater separation can be created between the undesired background noise and the desired speech signal before the sounds are sent into the ear and processed by the brain.